封装对大功率半导体激光器阵列热应力及Smile的影响

Effect of Packaging on Thermal Stressand Smile of High Power Semiconductor Laser Arrays

提出一种采用双铜-金刚石的"三明治"封装结构,利用有限元分析方法研究了其与传统的Cu+Cu W硬焊料封装结构激光器的热应力与Smile.对比模拟结果发现新封装结构热应力降低43.8%,Smile值增加95%.在次热沉热膨胀系数与芯片材料匹配的情况下,使用弹性模量更大的次热沉材料,可对芯片层热应力起到更好的缓冲作用.以硬焊料封装结构为例,分析了负极和次热沉厚度对器件Smile的影响.结果表明负极片厚度从50μm增加到300μm,器件工作结温降低2.26℃,Smile减小0.027μm,芯片的热应力增加22.95 MPa.当次热沉与热沉的厚度比小于29%时,Smile随次热沉厚度增加而增加;而当次热沉厚度超过临界点后,Smile随次热沉厚度增加而减小.当次热沉厚度达到临界点(2300μm)时,硬焊料封装的半导体激光器具有最大的Smile值3.876μm.制备了Cu W厚度分别为300μm和400μm的硬焊料封装976 nm激光器,并测量了其发光光谱.通过对比峰值波长漂移量,发现Cu W厚度增加了100μm,波长红移增加了1.25 nm,根据温度和应力对波长的影响率可知应力减小了18.05 MPa.测得两组器件的平均Smile值分别为0.904μm和1.292μm.实验证明增加Cu W厚度可减小芯片所受应力,增大Smile值.

A ″sandwich″ structure based on copper-diamond is proposed,the thermal stress and Smile of the proposed structure and traditional Cu ＋ Cu W hard-solder packaged laser are studied by finite element analysis.Comparison of simulation results shows that the thermal stress of the new package structure is reduced by 43.8% and the Smile value is increased by 95%. When the coefficients of thermal expansion of laser chip and submount are matched,the submount materials with larger elastic modulus can better buffer the thermal stress of the chip. Taking the widely used Cu ＋ Cu W hard-solder package structure as an example,the influence of negative electrode and substrate thickness on the Smile of diode laser chip is studied. It shows that when the thickness of the negative electrode increases from 50 μm to 300 μm,the junction temperature of the chip decreases by 2. 26 ℃,the Smile value decreases by 0. 027 μm,and the thermal stress increases by 22. 95MPa. When the thickness ratio of the substrate to the heat sink is less than 29%,the Smile value increases with the increase of the thickness of the heat sink,and when the ratio exceeds the critical point,the Smile value start to decrease. Hard-solder packaged semiconductor lasers have a maximum Smile value of 3. 876μm at a critical thickness of 2300 μm. Hard-solder packaged 976 nm lasers with Cu W thicknesses of 300 μm and 400μm are fabricated. The luminescence spectra are measured. By comparing the peak wavelength shifts,it is found that when the Cu W thickness increased by 100 μm,the red shift of wavelength increased by 1. 25 nm.According to the effect of temperature and stress on the wavelength,the stress is reduced by 18. 05 MPa; the average Smile values of the devices are also measured,which are 0. 904 μm and 1. 292 μm respectively.Experiments show that the increase in Cu W thickness can reduce the stress in the chip,but increase the Smile value.